Contrast-agent-assisted images are recorded by imaging methods such as magnetic resonance tomography (MRT) and computed tomography (CT) primarily for diagnostic purposes. The contrast agent is administered to the patient prior to the recording of a diagnostic image and permits imaging with specific contrast, in particular in order to observe perfusion processes.
For contrast-agent-assisted recording of diagnostic images it is important that the recording is carried out at the right instant in time. If the diagnostic image is recorded too early or too late, it will not be possible to derive the desired information from the recording.
In order to determine the right time instant for the recording of a diagnostic image, test images are recorded as a means of monitoring the uptake of the contrast agent. Typically, the test images are recorded at intervals of a few seconds, and from them is derived what is termed a bolus value which characterizes the uptake of the contrast agent. The actual recording of a diagnostic image is started if the bolus value exceeds a threshold value.
A problematic aspect is that if the frequency with which the test images are recorded is low, then the temporal resolution for determining the time instant at which the bolus value exceeds a threshold value will also be low. Conversely, a high test image recording rate is at the expense of increased cost, time and effort, and, in the case of an x-ray examination, also an increased dose for the patient.
A method for bolus tracking is known from US 2010/0249582 A1. This method entails the recording of a baseline image or a plurality of baseline images as well as an automatic establishment of a trigger region or a plurality of trigger regions within the one baseline image or within each of the plurality of baseline images. The method also includes the checking of the automatically established trigger region or trigger regions for the arrival of a bolus in the trigger region or in the plurality of trigger regions. The method furthermore includes the forecasting of the arrival of the bolus in a selected volume, based on the arrival of the bolus in the one trigger region or in the plurality of trigger regions, as well as the acquisition of a diagnostic scan in the selected volume at the forecasted time.